get autovacuum mode from db header on existing dbs

if autovaccum on, look for ptrmap pages

core/lib.rs

@@ -40,6 +40,7 @@ pub mod numeric;
 mod numeric;
 
 use crate::storage::checksum::CHECKSUM_REQUIRED_RESERVED_BYTES;
+use crate::storage::pager::{AutoVacuumMode, HeaderRef};
 use crate::translate::display::PlanContext;
 use crate::translate::pragma::TURSO_CDC_DEFAULT_TABLE_NAME;
 #[cfg(all(feature = "fs", feature = "conn_raw_api"))]
@@ -549,6 +550,29 @@ impl Database {
         pager.enable_encryption(self.opts.enable_encryption);
         let pager = Arc::new(pager);
 
+        if self.db_state.is_initialized() {
+            let header_ref = pager.io.block(|| HeaderRef::from_pager(&pager))?;
+
+            let header = header_ref.borrow();
+
+            let mode = if header.vacuum_mode_largest_root_page.get() > 0 {
+                if header.incremental_vacuum_enabled.get() > 0 {
+                    AutoVacuumMode::Incremental
+                } else {
+                    AutoVacuumMode::Full
+                }
+            } else {
+                AutoVacuumMode::None
+            };
+
+            pager.set_auto_vacuum_mode(mode);
+
+            tracing::debug!(
+                "Opened existing database. Detected auto_vacuum_mode from header: {:?}",
+                mode
+            );
+        }
+
         let page_size = pager.get_page_size_unchecked();
 
         let default_cache_size = pager

core/storage/btree.rs

@@ -5887,6 +5887,7 @@ pub(crate) enum PageCategory {
     Overflow,
     FreeListTrunk,
     FreePage,
+    PointerMap,
 }
 
 #[derive(Clone)]

core/storage/pager.rs

@@ -2591,7 +2591,7 @@ impl CreateBTreeFlags {
 **               identifies the parent page in the btree.
 */
 #[cfg(not(feature = "omit_autovacuum"))]
-mod ptrmap {
+pub(crate) mod ptrmap {
     use crate::{storage::sqlite3_ondisk::PageSize, LimboError, Result};
 
     // Constants

core/vdbe/execute.rs

@@ -7974,6 +7974,31 @@ pub fn op_integrity_check(
                         expected_count: integrity_check_state.freelist_count.expected_count,
                     });
                 }
+
+                let auto_vacuum_mode = pager.get_auto_vacuum_mode();
+                if !matches!(
+                    auto_vacuum_mode,
+                    crate::storage::pager::AutoVacuumMode::None
+                ) {
+                    tracing::debug!("Integrity check: auto-vacuum mode detected ({:?}). Scanning for pointer-map pages.", auto_vacuum_mode);
+                    let page_size = pager.get_page_size_unchecked().get() as usize;
+
+                    for page_number in 2..=integrity_check_state.db_size {
+                        if crate::storage::pager::ptrmap::is_ptrmap_page(
+                            page_number as u32,
+                            page_size,
+                        ) {
+                            tracing::debug!("Integrity check: Found and marking pointer-map page as visited: page_id={}", page_number);
+
+                            integrity_check_state.start(
+                                page_number as i64,
+                                PageCategory::PointerMap,
+                                errors,
+                            );
+                        }
+                    }
+                }
+
                 for page_number in 2..=integrity_check_state.db_size {
                     if !integrity_check_state
                         .page_reference